The term "disposable nappy" or "nappy pants" is generally understood to mean a product generally intended to be used once and comprising a sheet of flexible impermeable material such as polyethylene, a flexible pad of absorbent material on one of the sides of this impermeable sheet and generally a sheet of permeable material such as a non-woven textile material covering the pad. The arrangement is generally supplied flat and thus, when flat, is in the shape of a rectangle whereof the longer edges are sometimes cut out in a central area to define a narrow portion, the product also being able to be folded over on itself in the form of a Z in the vicinity of its two longer edges, by folding the side regions onto the area defined by the permeable material. When the product is placed on the baby, the central region which is possibly narrower is placed between the baby's legs and its regions located on either side of this central region are placed respectively in front of and behind the baby, then these two end regions are partly overlapped on the baby's sides where they are interconnected for example by means of self-adhesive tabs. When the nappy is put in position, each of the longitudinal edges of the product overlap on one side of the baby thus defining a loop which constitutes the periphery of a passage for the baby's leg, whereas the transverse edges respectively define the front and rear parts of the waist of the product, which is thus substantially in the form of pants.
A product of this type has numerous variations, but none of these variations overcomes two considerable drawbacks of this product.
The first of these drawbacks consists of an inadequate seal in the region of the thigh. In fact, it is apparent that contact between the central region of the longitudinal edges of the product and the baby's leg is neither sufficiently firm, nor sufficiently flexible to ensure a seal in this region particularly when the baby is moving. Even if care is taken to press this region against the baby's skin when the disposable nappy is put in position, in view of the fact that the pressure applied to the skin should not be excessive, the slightest movement of the baby is sufficient to cause the appearance of an opening causing leakages.
A second drawback of currently known products resides in the fact that even if it is possible to adjust at will the pressure at which the two edges of the product defining the waist are pressed against the baby's skin, this adjustment undertaken at the time of fitting the nappy, does not necessarily prove satisfactory thereafter. In fact, a baby's waist measurement varies rapidly, in practice several times during a day, in particular in the course of digestion. Thus, a waist which is suitably adjusted when the nappy is put in position, may subsequently prove too restricting, for example when the baby eats after the nappy has been put in place, or on the contrary, may prove too wide after a certain period of time for digestion. In the first case, wearing the nappy may become painful for the baby and anyhow, in either case, the disposable nappy does either because the waist tends to reach a narrower part of the body, or because this waist is no longer adequately secured, which on the one hand allows the passages for the legs to open and consequently accentuates the above-mentioned inadequate seal and on the other hand gives the disposable nappy a disorderly shape which is both unattractive and uncomfortable.